1. Field of the Invention
The present invention relates to upright vacuum cleaners and, more particularly, concerns power assisted upright vacuum cleaners.
2. Description of the Prior Art
Of the various types of vacuum cleaners, one is an upright vacuum cleaner. The upright vacuum cleaner generally includes a base unit attached to a shaft/handle structure designed to be moved as an entire unit along a floor covering, such as carpet, in order to suction up dirt, debris, and other objects. The base unit of the upright vacuum cleaner is supported on an axle having two wheels, and includes an operating motor that drives an impeller to provide suction to the base unit so that dirt, dust, and other debris or particulate matter from the floor can be deposited in a disposable bag. The base unit additionally includes a rotating agitator brush which also makes contact with the floor to assist in the cleaning process. The agitator brush is generally connected to the drive or suction motor via a belt so as to rotate the agitator brush when the impeller and vacuum cleaner is on.
In those vacuum cleaners of the prior art that do not have an internal drive system so as to be power assisted or self propelled, the vacuum cleaner is manually moved by the operator along the floor by exerting a pushing or pulling motion on the handle and shaft generally pivotally connected to the base unit. A considerable amount of force may be required to push or pull the vacuum cleaner over certain floor coverings, especially carpets such as deep pile or shag carpet. In addition, many of the vacuum cleaners are relatively heavy due to the weight of their operating motors and other components. Because of this, many vacuum cleaners have been provided with an internal drive system to assist the operator in propelling the cleaner in forward and reverse directions.
These power assisted vacuum cleaners generally comprise an internal drive system disposed within the base unit including some type of transmission. Transmissions of the prior art have included independent bidirectional motors which engage the drive wheels to provide forward and reverse driving modes, and operator controlled clutches providing forward and reverse driving modes connected to the vacuum cleaner suction motor via a belt or gear arrangement. In all cases, the transmission forming a part of the drive system is mounted integrally with or directly on the axle of the drive wheels, or alternatively connected to the axle of the drive wheels via belts and pulleys. In the case of transmissions incorporating operator controlled clutches, the drive system is made rotationally operable through connection of the vacuum cleaner suction motor with the transmission via belts and pulley or gears. Thus, since the transmissions of the prior art are all connected to the vacuum cleaner suction motor, the drive system cannot be slowed down without decreasing the speed of the suction motor, consequently decreasing the suction power of the vacuum.
The bidirectional motors of the prior art suffer from jerking motion and rough start up, since the motor must reverse its rotational direction when the operator wishes to change from a forward to a reverse direction or from a reverse to a forward direction. The rapid and recurrent direction changes associated with vacuum cleaning in general reduces the brush life and the overall life expectancy of the motor, as well as being tiresome to the operator.
Typically, the internal drive system is placed in either a neutral or inoperative mode whenever the drive wheels are not to be driven or in an operative mode whenever the drive wheels are to propel the cleaner, either in a forward or reverse direction. The modes of the drive system are determined, in some vacuum cleaners of the prior art, by the movement of a slidable handle grip on the distal end of the handle shaft. The handle grip is to connected to a Bowden or other type of sheathed cable which is in turn connected to the transmission unit of the drive system. Thus, when the operator pushes the vacuum cleaner in the forward direction the handle is pushed forward moving the attached cable forward thereby engaging the drive wheels in the forward direction, when the operator pulls the vacuum cleaner in the reverse direction the handle is pulled backward moving the attached cable such that the drive wheels are engaged in the reverse direction.
The control systems of the prior art, however, were abrupt when changing directions as the transmission was either fully engaged or disengaged. Further, there was a tendency to have a slapping action thus giving a jerking motion or feeling when the control systems of the prior art engaged the transmission.